Within the field of telecom apparatuses, such as base stations for mobile telephony and terminals for mobile datacom equipment there is a need for switches and relays that provide high isolation typically exceeding 80 dB.
Micro mechanical switches (MEMS) constitute a promising technology for providing miniaturised switches on for instance Silicon substrates. This technology, however, still leaves something to be desired concerning the required high isolation. The following documents are examples of MEMS.
Prior art document U.S. Pat. No. 6,057,520 discloses an electrostatic operated device comprising a substrate, an insulating layer, and a substrate electrode for providing repulsive forces and an insulating layer. A movable electrode is of flexible material is deposited on the planar surface such that a distal portion can curl away from the planar surface. Two composite layers with different thermal coefficients of expansion will also curl the electrode.
U.S. Pat. No. 6,124,650 shows a MEMS magnetic actuation device comprising a latchable cantilever on which a soft latchable magnetic member is placed and a plane coil for moving the cantilever. Both the cantilever and the coil are mounted on a thin field substrate. This document moreover mentions that thermal; magnetic and electrostatic MEMS relays are known in the art.
U.S. Pat. No. 5,475,318 shows a micro-cantilever with an integrated heating element comprising fist and second layers, such as silicon dioxide and aluminium, of different coefficients of thermal expansion. The micro-cantilever has a tip, which is brought into contact with a material for measuring friction during atomic force microscopy.
U.S. Pat. No. 6,100,477 shows a MEMS electrostatic RF switch having a membrane, which is attached, by respective flexure structures, in two opposite ends to a substrate.
U.S. Pat. No. 5,959,338 discloses an electrostatic relay mounted on a silicon wafer. The relay comprises an upper poly-silicon diaphragm, a central electrode and a lower poly-silicon diaphragm. A conductive depression in the wafer and a conductive portion of the lower diagram will make contact due to electrostatic forces.
WO9936948 discloses a micro-mechanical device manufactured on a silicon substrate. On the silicon substrate, silicon dioxide layers are formed for etching material and releasing meander shaped cantilever beams. A top metal layer is sputtered on the silicon dioxide layer. The top metal layer extends to vertical sections on the cantilever beams.